Amplifier for electrically-disturbed telephone lines



May 31, 192?. LSBQfii M. LATOUR AMPLIFIER FOR ELECTRICALLY DISTURBED TELEPHONE LINES Filed Aug. 29, 1921 s Sheets-Shet 1 May 31, 1927. 1,630,346

M. LATOUR AMPLIFIER FOR ELECTRICALLY DISTURBED TELEPHONE LINES Filed Auz. 29, 1921 s Sheets-Sheet 2 r/u en 5 y M. LATOUR AMPLIFIER FOR ELECTRICALLY DISTURBED TELEPHONE LINES Filed Aug. 29. 1921 -5 Sheets-Sheet 3 Patented May 31, 1927.

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mamas Ln'rouaor rams, Eamon, nssrenon'ro tn'roun. oonronnrron, or innsniz i 1 our, NEW JERSEY, A conromrron or DELAWABE.

mrnzmrnn r02. nLEo'rRIcAnLY-msrUBBnnrntnrnonn LINES. Application filed August 29, 1921, Serial No. 496,649; and in mite, aim-5,1915. (GRANTED uiuma rnn rnovr'sron's or THE new or MABCH'3, 1921, 41 srA'r'. twists.)

The present invention relates improvements in telephone systems, and m particular telephone lines sufiering from disturb ances consequent upon the induction therein of parasitic currents as in highly attenuated lines. It is more particularly described with reference to the accompanying diagrammatic drawings, Figs. 1 to 10, inclusive.-

Figure 1 illustrates the invention as applied directly to the terminals of an interurban line;

Figs. 2, 3, 4:, 5 and 6 illustrate various modes of applying the invention to a twowire interurban line having a two-wire subscribers line connected to its extremity;

vention. a

Several typesof amplifiers have been devised with a view to compensating forthe attenuation of the speech signals during their propagation along the line. These re? peaters, as they are commonly called, are in troduced in the telephone line, usually midway between the terminal stations, and areso arranged as to permit of amplifying the speech signals emanating from either end of the line; hence the name two-way tworepeater by which "they are desi ated. They all suffer from the same defect t at, inasmuch as they are. situated at a point of the line where the speech signals have al ready undergone attenuation, they amplify prevail in the telethe anode circuit being energized by the sup-.

ply 3. The grid-filament circuit is influenced by the secondary winding of an input transformer 4 the primary winding of which is included in a circuit comprising a cell ,5 and a microphone 6. The secondary winding of microphone 6. 1 1 As far as the amplified microphone cur-- Figs. 7, 8, 8", 9 and 10 illustrate various means of adapting the interurban line to etIicient working with the main part of the innot only the signal currents, but also the the output transformer? feeds thetelephone line at terminals 8 as well as the artificial real line. i v

The receiver 9,-which'is shunted by animpedance 10, -is connected between the junct1on pointof the real and artificial lines-on one side and a point intermediate-the ex tremitles of the secondary windin "of. the

output transformer on the other si e. The

object "of the latter arrangementis to avoid the so-called howling or Larsen" effect caused by the reaction of the "receiver-'9 rent is concerned, the receiver 9 may-thus be connected to ,equi otentialpoints.- In this manner thegampli ed current does not affect the receiver'9 which, would be apt to react onthe mlcrophone 6 and thereby set up howl v y p v ing. The artificial line llfis variable as' w'ell as ing of the output transformer 7 upon the the tapping pointonlthe secondary'windplified speech of the correspondmgparty to a normal value and, at the same time, at-

-' tenuate the effects of the disturbances in-' duced in the line. 4 7

Instead. of shunting the receiver 9-only, either'another resistance 18 or 'a capacity 17 ma be inserted in series with the'rec'eiver 9,

an the shuntingimpedance 10 may or may not be made to shunt the receiver-resistance or receiver-capacity system 'thl1S formed.

This is shown in Fig. 6.

With the same object inview, it is ossible to use a receiver which is not suite tothe circuit by having a toohigh or too low impedance.

Another method consists in the systematic use of a high resistancetele hone line that could be made up, for ex'amp e,'of small copper wire or of a more electrically resistive conductor, such as iron, so as to reducethe value of the induced disturbances.

The use of transmit-tin amplifiers at the ends'of the line will a ways insure telephone currents,

properly speaking, of a' suflioient value.

As illustrated in Fig. 7, an appropriate impedance 14 can be put in series or in shunt with the real line so as to dampen the cur-x rents circulating therein. The increase of under very attenuated intensity. The object.

being attained, terminal transmitting amplifiers are then used to allow of telephonic communication being carried on over the ineficient telephone line thus realized.

The invention has so far been described in combination with a circuit arrangement suitable to eliminate the so-called howling or Larsen efiect. Failing the adoption of this particular arrangement, however, the receiver 9 can be branched in shunt the transformer 7 or, as shown in Fig. 9, it can be actuated b a special. winding 19 ofthe output trans ormer having a suiliciently small number of turns to prevent the incombination duced currents from disturbing the reception of speech.

Instead of being fed directly, the telephone line 8 can be fed through a so-called transformer 16 as shown 1n Fig. 10 and having a ratio such that the in- 35 .duced disturbing currents are very attenuated in the receiver circuit.

The subscriber can. be connected with the terminal amplifying station by two wires only, instead of by four wires, as would be required with the' arrangement illustrated in Fig. 1. Figs. 2 and 3 illustrate two practical methods of realizing this. The reference numbers in the latter figures are used to designate the same organs as in Fig. 1.

In Flgs. 2 and 3, the thermionic tube amplifier l is energized by the batteries 2 and 3. The amplifier further includes an input transformer 4 and an output transformer 7.

The interurban telephone line is connected to the termina s 8 and a variable artificial line is connected at 11. The subscribers line is connected at 12.

F i 2 illustrates the series arrangement whic may include an impedance 10 whose function is to just as in Fig.

Fig. 3 illustrates the shunt arrangement and is shown to include the shunting imshunt the received current pedance 10.

Instead of obtaining a balance by means of the artificial line 11 only, that is, by balancing the output circuit only, an additional balance may be also obtained by adjusting the input circuit. Figs. 4 and 5 illustrate two methods of realizing this. The ref- Instead of inserting series imerence figures therein'have the same meaning as in the preceding figures.

In the case of Fig. 4, the interurban telephone line is connected with the subscribers line through a transformerlO the primary of which is connected between two equi-v potential points from the amplified current point of view. In series with the subscribers 'line there is a balancing. impedancelii adjusted to a value equal to that of the subscribers line. The primary of the input transformer 4 is then connected between two equipotential points from the point of view of telephone currents received from the interurban line and sent on to the subscriber via transformer 10.

In practice, it is possible to use either an autotranslormer or an impedance with a middle-point in place and stead of transformer 10 as shown in Fig. 5.

Fig. 5 represents the more usual way of using the invention and includes a simple resistance 10?. -This resistance also contributes to attenuate the parasitic currents inasmuch as it decreases the audibility.

It is to be remarked that, in the case of Fig. 4 as well as in that of Fig. 5 by adding the balancing efiects of the two artificial lines 11 and 13, it is possible to more closely approach the condition of. minimum value of the amplified current apt to traverse the primary of the transformer ,4.

It is not ,intended to restrict the degree of amplification to a single thermionic tube as shown in the accompanying figures merely by way of example, but any number of such tubes may be used to obtain'thespeech amplitude required to produce a normal audibility at the far end of the line.

According to the invention, the amplifying systems are placed at the extremities of the interu-rban line. In the case of a telephone system which undergoes disturbing effects over only a portion or, its circuit, however, the amplifying. systems would then be laced at the input and output ends of the d sturbed portion of the system.

What I claim is 1. In combination, a thermionic tube transmitting amplifier at each end thereof, and means for reducing the audibility of the parasitic currents and,

speech in said line.

2'. A method of reducing the efi'ect of electrical disturbances on telephone linescharacterized by, the initial amplification of speech'currents simultaneously with a reduction of the received currents.

3. In a long distance telephone communication system, a two-wire interurban line a two-wire subscribers line at each end oi said interurban line, an outgoing transmitting amplifier interposed between each. of said subscribers lines and the interurban line, an incoming receiving transformer in telephone line, a

terposed between each of said subscribers lines and the interurban line in circuits forming a shunt around said outgoing amplifier, means at each extremity including an artificial line to balance the inter-urban line, and means at each extremity including an artificial line to balance said subscribers line.

4. In a long distance telephone communication system having a two-wire interurban line, a two-wire subscribers line at each extremity of said interurban line, an outgoing transmitting amplifier between the interurban line and each of said subscribers lines, an incoming receiving circuit shunted around each of said amplifiers, and artificial lines at each extiemity of said interurban line to balance said interurban and subscribers lines, the method which comprises employing both of said artificial lines to balance out the eflect of the plate .circuit of each amplifier upon its grid circuit.

5. The method of reducing the relative effect of induced current to voice current in telephone circuits, which consists in amplifying the voice currents to an abnormal value before they enter the region of induction and reducing them to a normal value and simultaneously reducing the induced currents after they leave the said region to such an extent that the disturbing current becomes inappreciable in magnitude.

(3. In combination, a plurality of transmission lines, one being subject to the inductive influence of the other, transmitting and receiving devices associated with the terminals of the said one line, an amplifying device associated with said line substantially between the transmitting device and the region of inductive influence, and an attenuating device associated with said line substantially between the said region and the receiving device, said attenuating device simultaneously attenuating both currents to such an extent that the disturbing current becomes iii-appreciable.

7. In a telephone.transmission line having terminal apparatus associated thereto, the method of reducing the interference in the telephone circuits of said line, which consists in amplifying voice currents flowing from the terminal apparatus to an intermediate point on said line to such an extent that the interference currents encountered are negligibly small as compared with said voice currents, and in attenuating the voice and the interference currents flowing from an intermediate point on said line to the terminal apparatus to normal value for the voice currents.

8. The method of reducing interference in transmission systems, which consists in amplifying only such energy as flows in a circuit towards the region of disturbance and in simultaneously attenuating all the energy which flows in said circuit in the opposite direction as to "the disturbances to such an extent that the interfering energy becomes small.

9. The method of reducing disturbance in a signal transmission system havinga source of disturbing energy associated therewith, which consists in amplifying the signaling energy above normal transmission level before the same reaches the source of dist urbing energy and subsequently attenuating said signal and disturbing energy to such an extent that said signal energy reaches normal transmission level.

10. The method of reducing interference in transmission systems, which consists in modifying the energy flowing in a medium toward the region of disturbance by a different factor than for the energy flowing in the opposite direction in said medium.

11. The method of reducing interference in transmission systems, which consists in modifying the energy flowing in a medium toward the region of disturbance by a higher factor than for that flowing in the opposite direction in said medium.

12. In a two-way telephone transmission line, the method of reducing interference, which consists in amplifying signal currents flowing from either end to the line above normal transmission level and attenuating said signal currents flowing from the line to either end back to normal transmission level.

13. A telephone transmission line, substations associated therewith at its ends, a repeater between each substation set and the line, said repeaters comprising means to amplify currents flowing to the line and to attenuate currents flowing from the line to ward the substations.

14. A telephone transmission line, suosta tions associated therewith at its ends, a repeater between each substation set and the line, one side of said repeater comprising an amplifying element for the current flowing to the line and the other side comprising an attenuating element for current flowing from the line.

In testimony whereof I aflix my signature.

MARIUS LATOUR. 

